There stars that would otherwise have been blocked


There are
several important pieces of evidence that support the Big Bang theory. Among
them, the two most prominent are Big Bang nucleosynthesis (BBN), a process
responsible for the creation of almost all the hydrogen we see in the universe
today, and the cosmic microwave background (CMB), which is electromagnetic radiation
left over from the formation of the universe. Prior to being observed, the cosmic
microwave background was first predicted in connection with the work of Ralph
Apherin, George Gamow, and Robert Herman on BNN in 1948. (NASA/WMAP Science Team, 2016) However,
it wasn’t until many years later that sufficient technological advancements could
search for the evidence, and verify these hypotheses.

Big Bang, or
primordial nucleosynthesis, is believed to have taken place from approximately
10 seconds to 20 minutes after the Big Bang. (“Primordial Nucleosynthesis,”
n.d.) The universe was hotter than the centre of a star, and nuclear fusion
allowed the nuclei of “light elements” to form from protons and neutrons, despite
it being too hot for electrons to join these nuclei. These ions would later
form neutral atoms when the universe had cooled sufficiently as a result of
expansion. The Big Bang theory predicts the exact proportions of “light elements”
like hydrogen, helium, lithium, and deuterium that would have been created as a
result of these specific conditions. (Jenks, 2014, 0:55)

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The
current elemental composition of the universe is identifiable using the
electromagnetic spectrum. Each element has its own unique spectral signature,
which can be used to identify the nature of stars, as well as other celestial
bodies, and in turn what the universe is made of. Technology like the Hubble
Space Telescope allowed astronomers to see light from distance stars that would
otherwise have been blocked by Earth’s atmosphere. Using Hubble’s Wide Field
Camera 3 and spectral emission data, scientists were able to identify the
percentage of elements that are abundant in today’s universe. (May, 2017) It
was found that the universe is made of approximately 75% hydrogen and 25%
helium, and the remaining elements make up less than 1%. In addition, tests at
laboratories and particle research facilities have recreated the environments
and energy levels present at the time of nucleosynthesis in order to determine
whether these elements could have been formed under these conditions. (O’Dowd, 2016, 7:20)
Comparing the predictions from Big Bang theory with the data gathered by
astronomers and astrophysicists, the accuracy to which the theory predicts the
percentages of each element is incredible. It is in direct agreement with the
composition proposed in the Big Bang theory.

The cosmic
microwave background is thought to have been created 400,000 years after the
Big Bang (and subsequently BBN) first took place. At this time the universe was
still extremely hot and dense. These conditions made it impossible for atoms to
form, and instead free electrons, and nuclei made of protons and neutrons, were
scattered throughout the relatively small universe. This created an opaque plasma
in which photons were unable to travel freely, as they would bounce off free
electrons and remain trapped. The CMB was created in a period of time known as
the Recombination Era, when the universe had cooled to a sufficient temperature
of approximately 3000K, and elements were then able to form. Subatomic
particles fused to form the element hydrogen, and because there were no longer
free electrons floating through space, the photons were able to escape. This
surface, where the universe transitioned from opaque to transparent, is know as
the surface of last scattering. (Tate, 2013) These photons have been travelling
through the universe ever since. Having been stretched out to infrared waves and
then eventually microwaves as a result of travelling through expanding space,
they give us an image of what our universe looked like at 400,000 years old. The
Big Bang theory predicts that the currently observable microwave background
radiation should have cooled to a temperature of about 2.7 degrees kelvin. (O’Dowd, 2016, 4:13)

Evidence for
CMB radiation was first accidentally discovered by Arno Penzias and Robert
Wilson in 1965 while the two were working at Bell Telephone laboratories in
Murray Hill, New Jersey. They had constructed and were using a radiometer for
experiments involving satellite communications and radio astronomy. However,
they soon noticed their antenna picking up a background noise of about 2.7
degrees above absolute zero in every direction that neither Penzias or Wilson
could account for. (NASA/WMAP
Science Team, 2016) They began troubleshooting to find the source, ruling
out both urban and military radio interference, and even going as far as to
remove pigeons who had been nesting in the radio antenna. It was around this
time that the two heard about the work of physicist Robert Dicke at Princeton
University. His research suggested that there should be a residual radiation
throughout the universe left over from the Big Bang, and he was planning on
testing his hypothesis. Both groups independently published their findings in a
scientific journal, and in 1978 Penzias and Wilson received the Nobel Prize in
Physics for the discovery of the CMB. (Levine, 2009)

Much
later, in the 1990’s the COBE (Cosmic Background Explorer) satellite was
launched in order to attain a higher resolution microwave image of the CMB, and
was able to do so with an accuracy of 0.005% over the entire visible sky. This
led to the important discovery that the radiation is uniform throughout the
universe, with very little deviation in temperature. These slight deviations are
believed to have caused galaxies to form. (COBE, 2015)

Scientists
studying Big Bang theory continue to gather data and perform experiments as
technology becomes more powerful, but the major milestones in the discovery of evidence
to support Big Bang nucleosynthesis and the cosmic microwave background cannot
be overstated. 

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